The burgeoning electronics industry has been driven by consumer and commercial needs for more and more complex electronic assemblies in ever smaller spaces. With the conversion from vacuum tubes to integrated circuits, electronics transitioned from individual hand-wired components on a major chassis to printed wiring board (PWB) assemblies with integrated circuit subassemblies thereon. In the early days of electronics, virtually all of the electronic parts were interconnected by wires routed primarily on the underside of the chassis. As transistors, and then integrated circuits, came into widespread use, it became possible to group major electronic functions together on designated areas of the chassis. The chassis evolved to a "motherboard" when it became possible to move some functions to smaller PWBs or "daughterboards." The terms "motherboard" and "daughterboard" in this context are not limited to computer applications but include any electronic devices with PWBs that function in the general manner described.
PWB assemblies comprise a substantially flat, rectangular package having two parallel major surfaces and a number of minor surfaces, or edges, normal to the major surfaces. The major and minor surfaces are designated as such to indicate that a surface area of the major surface is greater than a surface area of the minor surface. Arbitrarily for the sake of this discussion, motherboards are considered to be mounted horizontally; however daughterboards, may mount horizontally or vertically. Of course, there are applications where the motherboard is vertical. Horizontal mounting places the major surfaces of the motherboard and daughterboard substantially parallel. Vertical mounting places the major surface of the daughterboard normal to the major surface of the motherboard. Vertical mounting also allows designers to package more electronics into less area of the motherboard, thereby reducing the overall footprint of the electronic devices. Therefore, some means of mechanically attaching and electrically interconnecting the PWB subassemblies/daughterboards to the motherboard is extremely important. Interconnecting the daughterboards for removable/replaceable functions, such as a modem, video card, disk drive controllers, etc., is usually accomplished by edge card connectors with friction fit contacts spaced 0.1" apart on center. Some daughterboard functional subassemblies, however, are essential to the overall function of the electronic device and therefore require permanent connection to the motherboard. Traditionally, permanently installed, single in-line packages (SIPs) are electrically connected to the motherboard with either plug connectors or edge card connectors that can be reflow soldered to the motherboard. Alternatively, electrical connections between the daughterboard and the motherboard may be accomplished with wire when the boards are mechanically coupled without electrical interconnnections. Of course, plug connectors, edge card connectors and wire connections add to the complexity and cost of the total assembly. Both of these techniques are expensive and have the additional disadvantage of unwanted inductance upon assembly.
Accordingly, what is needed in the art is an edge-mountable integrated circuit package and a method of attaching the package to a printed wiring board that minimizes both inductance, space and cost.